The present invention relates to a window in which a window sash is slidable upwardly and downwardly along side jambs of a window frame, and adapted to downward swinging toward the inside of the window frame. In a prior art, a counterbalance is employed to hold a window sash at a desired vertical position. As the counter balance, it is known that torsion force of a coiled torsion spring is used for counter balancing the window sash. To adjust the torsion force, there are known several mechanical structures wherein an adjusting shaft is restricted to rotate in one direction by a ratchet mechanism, or a braking force is applied to the adjusting shaft by resilient force of a coiled brake spring.
The former using the ratchet mechanism as mentioned above is convenient for winding the torsion spring, but inapplicable to unwinding it, whereby the torsion force can not be adjusted properly. The latter using the brake spring is applicable to the both of winding and unwinding of the torsion spring. However, due to unreliability of the braking force of the brake spring and reduction of the braking force by deterioration of the brake spring, the wound torsion spring is unwound naturally, which leads to out of use. Further, the winding and unwinding operations of the torsion spring are not made smoothly, and also the brake spring is not assembled readily.
Further, in a window in which the up-and-down slidable window sash is rotated from a vertical position to a horizontal position, there is known the use of a counter balancing apparatus comprising a counter balancing means for the window sash, and a braking means for applying a braking force to the window sash as the window sash is being inclined, to position it at a set inclined position.
In this counter balancing apparatus, the counter balancing means has no adjusting means for the counter balancing force, and thus it is impossible to adjust the counter balancing means after the counter balancing means and the window sash are assembled in the window frame, or to adjust the fluctuation of the force by the counter balancing means during operation.
In addition, there is known a window in which a sliding member is mounted on a side jamb of a window frame in an up-and-down slidable fashion, the sliding member is connected to the lower end of the window sash with a horizontal shaft such that the window sash would be swung inwardly in a horizontal direction, each of both sides of the window sash is connected to the sliding member with an arm to hold the window sash at a desired rotation angle in an inward direction, and a counter balancing means is disposed to hang the sliding member therefrom to hold the sliding member at a desired height.
The above arm is already connected undetachably to both the window sash and the sliding member which is slidable up-and-down within the side jamb of the window frame when such a window is made in a factory, and thus it is unavoidable to transport the window in a situation in which the window is assembled on the window frame, and this is inconvenient. Further, the counter balancing means can not be replaced readily after installation of the window, the downward swingable angle of the window sash toward the inside is restricted to a small angle for prevention of crimes, and when the area of the window sash is large the outside face of the window sash can not be cleaned readily.